Developer assembly for electrostatic copier

ABSTRACT

A developer assembly for conveying toner to be used in an electrostatic printing operation to a fur developing brush in small controllable quantities employs a plurality of contacting rolls which pick up toner from a toner sump and distribute it from one roll to another and then to a fur developing brush. An adjustable doctor blade is provided for removing excess toner from one of the intermediate rolls so as to finely meter the amount of toner ultimately transferred to the fur developing brush.

1451 Oct. 15, 1974 United States Patent 1 Howarth et a1.

3/1968 Lzlwcs ct all... 1/1971 Abe 2/1972 Klavsons ct a1... 6/1972 Primary Examiner-Morris Kaplan [73] Assignee: Zerox Corporation, Stamford, Conn. Attorney, g or mHi 1, r imp n, n Filed: g 1972 Santen, Steadman, Chiarra & Simpson [21] Appl. No.: 280,215

[57] ABSTRACT A developer assembly for conveying toner to'be used [22] in an electrostatic priming Operation to a fur develop 1 n S 24 ing brush in small controllable quantities employs a l plurality of contacting rolls which pick up toner from Field of Search.....................

346/74 ES; 355/3 DD; 117/17, 17.5, 21-23 a toner sump and distribute it from one roll to another and then to a fur developing brush. An adjustable doc- References Cited tor blade is provided for removing excess toner from UNITED STATES PATENTS one of the intermediate rolls so as to finely meter the XXX u u t we Qn fl em mw h GS 2,803,216 Termini et a1. $152,012 Schaffert......1.... 3,265,522

7 Claims, 4 Drawing Figures PAIENIEnnm 1 51914 SIEEI 10F 2 DEVELOPER ASSEMBLY FOR ELECTROSTATIC COPIER BACKGROUND, SUMMARY AND OBJECTS OF THE INVENTION In an electrostatic printer, it is necessary to provide a means for transferring toner to a fur developing brush which, in turn, contacts a charged paper drawn past the brush to ultimately transfer an image to the paper sheet.

Heretofore, it has been the common practice to provide means for dipping a wire in a toner bed and then moving the wire directly into contact with the fur developing brush. A second wire has been used to contact the periphery of the fur developing brush to provide for removal of excess toner but this system has not been completely satisfactory inasmuch as the toner has been rather irregularly applied to the brush in this fashion and the means for stripping excess toner from the brush has not provided uniform results. In addition, such intermittent wire contact with the brush causes damage to the brush and has a seriousadverse affect on .brush life.

In accordance with the'principles of the present invention an open cell foam sub-donor roll rotates continuously within a toner sump and makes surface contact with a toner roll which rotates in the same direction so that their surfaces are moving opposite one another at their point of tangency and this donor roll contacts, in turn, the fur developing brush. A doctor blade is placed in contact with the smooth outer surface of the donor roll intermediate the points of contact of that roll with the sub-donor roll and the fur developing brush so as to wipe off all excess toner from the donor roll before the brush is contacted. The donor roll and the brush likewise move in the same direction so that their surfaces are moving in opposite directions at the point of tangency.

In this manner the toner is uniformly applied to the fur developing brush and the transferable tonercoating on the donor roll can be maintained very thin so that not more than the desired amount of toner will actually reach the fur developing brush.

Separate means are provided for sufficiently agitating the toner within the sump so as to prevent the formation of pockets within the sump which would hinder the even distribution of toner to the donor roll.

The primary objective of the invention therefore resides in providing a means for positively and uniformly transferring toner from a sump to a fur developing brush and for doing it in a manner calculated to insure distribution of a thin even film of toner on the donor roll which ultimately contacts the brush.

BRIEF DESCRIPTION OF THE DRAWINGS Other objects, features, and advantages of the present invention, its organization, construction, and operation will be best understood from the following detailed description of the preferred embodiment thereof taken in conjunction with accompany drawings, wherein,

FIG. 1 is vertical sectional view of a developer assembly constructed in accordance with the principles of the present invention;

FIG. 2 is a vertical sectional view taken along the lines II-II of FIG. 1 and showing some parts in section and others in side elevation;

. trated in FIG. 1', and

FIG. 4 is a fragmentary side elevational view of the shifting mechanism for the toner agitator.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 illustrates the basic developer housing 9 and consists of a sump 10 defined by a sump wall '11 and two side walls 10a, 10b. A sub-donor roll 12, and donor roll 13, and a fur developing brush 14 are mounted therein for clockwise rotary movement about axes 15, 16 and 17, respectively.

Toner, such as is used in an electrostatic printing process, is an extremely finely powdered substance having many physical properties falling between those of a liquid and a finely powdered solid and this toner is placed within the sump 10 to such a level that it at least covers the sub-donor roll 15 and a portion of the donor roll 13. The sub-donor roll consists of an aluminum tube having hard nylon end caps (not shown) which, in turn, are mounted for rotational movement in the side walls 10a, 10b of the developer housing. The roll is covered with an open cell (highly porous) foam approximately oneeighth inch thick around the entire circumference of the roll. TheIsub-donor roll is caused to rotate in a clockwise direction(as viewed in FIG. 1) and in so rotating, it picks up toner from the sump and carries it on its foamed outer surface.

The donor roll 13 comprises an aluminum tube having a methyl terpolymer coating thereon which acts as a dielectric material between the charged donor roll and the electrically charged toner per se. The donor roll has a very lightly etched surface so that the roll not only holds toner attracted by the electric charge and by the affinity it has for the methyl terpolymer coating but also holds a slight amount of toner within the etched voids in the surface.

The diameters of the donor and sub-donor'rolls are such that the sub-donor roll has a designed diameter with about a one-eighth inch overlap on the donor roll as shown in FIG. 1 so that the foam surface of the subdonor roll is compressed at the point of tangency with the donor roll 13.

The fur developing brush comprises a large cylindrical roll formed of phenolic impregnated carboard or of other stiff material which has a rabbit fur pelt affixe thereto which in turn is designed to pick up toner from the donor roll and carry it to the charged paper drawn past the brush at the upper right corner of FIG. 1. The diameters of the donor roll and fur developing brush are such that there is significant overlap between their designed'diameters so that toner will be impressed into the fur as the brush rotates by compression of the brush pelt.

As heretofore noted, the sub-donor roll, the donor roll, and the fur developing brush all rotate in the same direction so that at their point of tangency the surfaces of the drums are rotating in opposite directions.

In order to insure that only a very thin film of toner is carried on the donor roll to the fur developing brush, a doctor blade 18 is provided. The doctor blade 18 is formed from a rubber-like material such as of silicone rubber, neoprene rubber, urathane, ethylene propylene, or rubber of the type which is used in automobile windshield wiper blades similar to those bearing the trademark Anco.

The doctor blade 18 is carried in an adjustable bracket 19 having an upstanding wall 20 which moves slidably within a groove 21 formed intermediate groove walls 22 and 23 in the housing. The relationship of the position of the element 19 and the manner in which the blade 18, itself, is seated is such that the doctor blade contacts the surface of the donor roll 13 at an angle of approximately 68 tangent the donor roll surface at the point of contact. In order to stand wear in use, the doctor blade has an appreciable thickness even at its point of contact with the donor roll and with this design the flat end of the blade is so disposed relative to the roll that only the sharp corner edge of the doctor blade contacts the roll.

The element 20 is movable along the wall of the grooves 21 so that the entire element and the doctor blade connected thereto can be removed from the housing for repair or replacement of the blade. The ele ment 20 has a spring member 24 connected thereto with an outwardly bent arm which takes on the appearance of a pen clip. The bent arm of this spring member contacts the lower edge 25 of an adjustment bracket 26 and serves to bias the element 20 downwardly within the groove 21 to impress the doctor blade 18 against the donor roll. An adjustment screw 27 is screw threaded through the upper wall 48 of the housing and engages the upper wall of the bracket 26 to oppose the bias of the spring 24 and provide a means for slidably moving the bracket 26 somewhat downwardly as may be desired to increase the pressure of the doctor blade on the donor roll.

An agitator shaft 30 is guided for longitudinal sliding movement within the sidewalls 10, 10b of the sump and has a series of wire-form elements 31 carries therealong in spaced relation to one another which are identically configured so as to include an arcuate portion 32 which extends over and in close proximity to a quarter arc portion of the sub-donor roll and so as to include an upstanding portion 33 extending adjacent and in close proximity to a portion of the donor roll immediately below the doctor blade 18.

As viewed in FIG. 4, the end of the shaft 30 extending through the wall 10b is fitted with a retaining washer 34 which serves as a seat for one end of a spiral-form spring 35 positioned intermediate the retainer 34 and the outer surface of the wall 10b. The shaft 31) is thus biased toward the right as viewed in FIG. 4 and the outermost end of that shaft has sliding contact with the flat cam surface 36 at a point displaced radially from the axis of the cam surface. The cam surface 36 is formed on a cam element 37 which, in turn, is mounted on a shaft 38 which is displaced from the axis of the shaft 31). The shaft 38 and cam 37 are mounted together for movement with a gear 39 which cooperates with a drive gear train so as to be driven rotationally.

It is important that the donor and sub-donor rolls be driven at a very slow peripheral speed and to this end it has even been found feasible to drive these members intermittantly rather than continuously. In any event, rotation of the element 37 causes the shaft 30 to be moved in and out to draw the wire-form elements 31 back and forth through the toner in the sump to prevent the formation of air pockets within the toner bed and to provide for even distribution of toner over the surface of the sub-toner roll. As the element 37 rotates, the shaft 30 is caused to move toward the left as illustrated in FIG. 4 and when the low point in the cam surface lies against the shaft 30 the shaft 30 is caused to move toward the right by the spring 35.

It will further be observed that an idler gear 40 is mounted on the sump wall 10b and meshes with gears 41 and 42, respectively, mounted on and in driving engagement, respectively, with the shafts 15 and 16. An additional gear train is provided to interconnect the elements 41D, 41 and 42 with the drive gear for the fur developing brush so that these members are all caused to rotate together or at least in timed relation to one another; continuous rotation of the brush being required.

The developer housing herein disclosed may ideally be utilized with a mobile electrostatic printer which may be carried from place to place and in order to prevent undue loss of toner from the assembly due to its being handled and jostled about, a foam seal 43 is carried by an aluminum extrusion 44 which, in turn, is mounted for sliding movement within cooperating grooves 45a and 45b and the foam itself has sliding contact with the surface of the smooth donor roll 13.

By the same token, top and front seals 46 and 47, respectively, are fitted on the upper wall 48 and sump wall 11, respectively, and extend out over the fur developing brush a distance just sufficient to permit the brush pelt to clear the seals without contacting them so as to prevent toner from being inadvertently thrown out of the housing.

The specific means by which the various members are driven and by which they are mounted for rotational movement within the housing itself have neither been shown nor described inasmuch as the particular means for accomplishing these functions are not considered to comprise a significant part of the inventive concept hereinafter claimed.

We claim as our invention:

1. An electrostatic developer assembly comprising:

a developer housing forming a toner sump;

a highly porous sub-donor roll comprising an open cell foam material disposed to move in juxtaposition to the bottom of said sump, a lightly etched polymer coated donor roll, and a fur developing brush mounted for rotary movement within said developer housing with said sub-donor roll positioned adjacent the bottom of said sump;

whereby said donor roll has surface contact with both said sub-donor roll and said brush to transfer toner from one to the other thereof;

means rotating said rolls and said brush in the same direction whereby the respective mating surfaces thereof move in opposite directions at their points of tangency and a resilient silicone rubber blade having edge contact with said donor roll for stripping excess toner from said donor roll prior to contact thereof with said brush.

2. An electrostatic developer assembly as claimed in claim 1 wherein means are provided for agitating toner within said sump.

3. An electrostatic developer assembly as set forth in ara}.,whetsini e ealient blfl i si iqaed n angle of approximately 64 tangent the donor roll surface at the point of contact.

4. An electrostatic developer assembly as set forth in claim 2 wherein means are provided for varying the from in spaced relation along the length thereof and means are provided for reciprocably moving the agitator shaft along its axis to agitate toner within said sump.

7. An electrostatic developer assembly as set forth in claim 6, wherein the wire form elements connected-to said shaft for agitating toner 'within said sump are spaced radially fromsaid sub-donor roll and generally conform to the contour of said sub-donor roll for a portion of the circumference thereof. 

1. An electrostatic developer assembly comprising: a developer housing forming a toner sump; a highly porous sub-donor roll comprising an open cell foam material disposed to move in juxtaposition to the bottom of said sump, a lightly etched polymer coated donor roll, and a fur developing brush mounted for rotary movement within said developer housing with said sub-donor roll positioned adjacent the bottom of said sump; whereby said donor roll has surface contact with both said subdonor roll and said brush to transfer toner from one to the other thereof; means rotating said rolls and said brush in the same direction whereby the respective mating surfaces thereof move in opposite directions at their points of tangency and a resilient silicone rubber blade having edge contact with said donor roll for stripping excess toner from said donor roll prior to contact thereof with said brush.
 2. An electrostatic developer assembly as claimed in claim 1 wherein means are provided for agitating toner within said sump.
 3. An electrostatic developer assembly as set forth in claim 1 wherein the resilient blade is positioned at an angle of approximately 64* tangent the donor roll surface at the point of contact.
 4. An electrostatic developer assembly as set forth in claim 2 wherein means are provided for varying the pressure with which said resilient blade engages said donor roll.
 5. An electrostatic developer assembly as set forth in claim 1 wherein said blade is positioned above the highest predetermined level occupied by toner within said sump and wherein means are provided for agitating the toner within said sump.
 6. An electrostatic developer assembly as set forth in claim 5 wherein the means for agitating toner within said sump comprise a shaft having plurality of wire form elements connected thereto and extending therefrom in spaced relation along the length thereof and means are provided for reciprocably moving the agitator shaft along its axis to agitate toner within said sump.
 7. An electrostatic developer assembly as set forth in claim 6, wherein the wire form elements connected to said shaft for agitating toner within said sump are spaced radially from said sub-donor roll and generally conform to the contour of said sub-donor roll for a portion of the circumference thereof. 